This invention relates to a composition and means for removing iodine and organic iodides from an iodine-containing off-gas stream and more particularly relates to a composition which may be utilized in iodine and iodide removal. Even more particularly, the invention relates to a method of making a sorbent material for removing iodine and organic iodides from iodine and organic iodide containing off-gas streams.
In the development of nuclear powered electric generating plants, many new types of pollution problems have arisen. In the processing of radioactive materials in these plants great concern has centered around the removal of radioactive iodine, iodine-131, and its organic forms, particularly methyl iodide, and prevention of the escape of the radioactive material into the atmosphere. Presently, several types of filtering and adsorbing devices have been developed for removal of these radioactive iodine materials, the most commonly used material presently available being impregnated activated carbons. These activated carbons have proved to be effective adsorbents but they have had disadvantages because of the ever present problem of auto-ignition due to decay heat at high loadings. It has further been noted that the adsorbing characteristics of the activated carbon deteriorate on purging of the process off-gas and the radioactive iodine will move through the carbon filter. Also, it has been noted that when the off-gas stream contains appreciable amounts of moisture, the adsorption efficiency of an activated carbon or charcoal filter is greatly diminished. On the other hand, non-combustible carriers have also been proposed wherein the carrier is an adsorbent material such as silver zeolite, silicas, and aluminas which have been impregnated with metal salts, specifically silver nitrate. However, the cost of these products have been found to be extremely high.